SmedSpeed XS650

 


CAMSHAFTS

Smedspeed now stocks performance cams for your stock phased engine. Using the very same high performance Landis 3L cam grinding machine that my rephased cams are manufactured on, I now offer reground camshafts. These cams utilise your existing cam core and have a performance profile ground onto it. The use of your stock core keeps the price down.  
The well renowned flat track Shell #1 and the early Yamaha XS1/XS2 profiles are available.

The cams are on an exchange basis, the cam given for exchange must be a usable core.

The cost is £150 exchange.


CAM PROFILES

I have 360 degree and 277 rephased EN40B billet steel cams available with any of the profiles listed below. All come with an adjustable sprocket, which facilitates changing the rpm at which peak torque occurs. This lowers or raises the power in the rev band.

ALL new billet cams are £304.00
(I also have reverse profile cams , if you wanted to reverse the cylinder head, very custom!)  

Yamaha XS1/ XS2 cam
Original equipment cam for 1970-1973. Nice cam for 650/750 strong low end and mid range. I use this a lot in 750 conversions, particularly where the engine will not be revved really hard. A lot of the aftermarket cams are too much for a 650cc engine,  this cam is not one of these.  Easy install.

Megacycle 250-20
Mild street cam. No pronounced power-band, relatively small improvements over whole rpm range. Not one of my favourites at all. 0.400’’ lift; there are much better cams than this.

Shell #1
The classic flat track cam, really good low end and midrange, good top end but not overly powerful at very high rpm. Easy install with 0.410’’ lift. Needs more compression on a 650 engine, or 750cc. Needs good valve springs.  

Yamaha race accessory cam
A direct copy of the Yamaha Race accessory cam available in 1972.  Lower lift means easy installation, not really much different from a Shell # 1. The cam Yamaha suggested you run with a 750 race kit.  

Megacycle 250-00
Street cam, improved mid range power needs higher compression than stock OR 750cc. Late inlet closing. 0.420" lift. Needs good springs.

Megacycle 250-30
A really good hot/wild street cam. 0.440’’ lift, needs 10:1 compression to work well, but gives very strong midrange and top end, and can be adjusted to give stronger bottom end too at the expense of some top end loss. Really good hot street cam for 750 cc and bigger engines. Needs shorter valve guides/valves recessing, and good valve springs.

Megacycle 250-40 
Race cam, drag racing, hill climbing, 0.480’’ lift needs 11:1 compression to make it work properly. A real race cam, don’t run this on the road, noisy valve gear, fast guide wear. Needs good springs, all clearancing work undertaken, not easy to install at all.


rocker arms and cam timing

When the Yamaha XS650 left the factory, the rocker arms were manufactured with a precisely ground radius on the area that contacts the cam and this was then hard chrome plated. Over many years the hard chrome wears, mostly due to extended oil changes, oil with no ZDDP in it, bad filtration and just general wear and tear (abuse). This wear has an adverse effect on the cam timing. Pictured below is a rocker arm I took out of a running engine. It did sound like a bag of bolts, but it was running nevertheless. This is the worst example I have seen, but many rocker arms which look good are not within specification, and the accumulated wear will only get worse over time.

Worn rocker arm

As part of my engine rebuilds, I dial in the cam timing using a degree wheel and a dial gauge mounted on the valve spring top collar. This way the cam timing can be set very accurately, and also any manufacturing discrepancy in the cam or the rocker arms can be traced. The performance and rephased cams I supply are ground on a Landis 3L cam grinding machine, many of the USA based cam manufacturers use this same equipment, it is state of the art, so I am entirely confident the cams are not the variable.

Landis 3L
 
I often find that my cam timing figures are not what I expect, sometimes way off what they should be, and this is invariably attributed to worn rocker arms. The chrome plating wears away and the radius "flattens" or small gouges are evident, all of which affect the valve opening duration, the cam lift strangely is essentially unaffected. To remedy the situation I have found a firm who can recondition the OEM rocker arms by replacing the radiused part of the rocker arm with a brazen on radiused stellite pad. This technology has been used to reclaim many thousands of Ducati rocker arms which also suffer the same fate as the XS650 items. The performance cams I provide are made from EN40B steel and then case hardened. The Stellite/EN40B is an ideal combination for a long lasting hard wearing valve gear.

Reconditioned rocker arm

So why bother at all I hear you say? There are many reasons for doing something properly, not least just to get it right. If you are fitting a new cam, whether it is for more performance or as part of a rephased engine build, it seems pointless not to do it the best it can be.

The engines I build are not in the main dedicated racing engines, just strongly built high torque engines. This increased torque allowed the bike to run higher gearing to cope with increased traffic speeds. Worn rocker arms translate the duration of what was a very mild cam in the first place into something more suitable for a lawn mower. A good mild street cam coupled with refaced rocker arms will really bring your engine to life.



Contact me for more details


DISCLAIMER
These are experimental parts intended for racing and as such no warranty is given or implied. If you decide to buy it is on the understanding that you assume complete responsibility for any possible injury, loss or damage that may occur as a result of using these parts and that you accept these conditions of sale prior to purchase.